Method and apparatus for improved trench box de-watering

ABSTRACT

A method and apparatus for use of a trenching or digging box which incorporates de-watering equipment that draws water into the lowermost portions of the box and pumps the water out of the box. This de-watering equipment can be retrofit into existing trench boxes by modification of the existing blade or lowermost portion of the box or the addition of a blade or lowermost portion. Slots or perforations in the blade portion or lower portions filter debris in the first instance. Additional or alternative filtering can be accomplished by lengths of perforated or slotted pipes inside the walls of the trench box, especially near the lower portions. Water can be drawn from either or both ends of the trench box. Attachments can be used to focus de-watering and specific areas of concern. De-watering can be from one or both of the side walls of the trench box.

FIELD OF INVENTION

The present invention relates to trench or “digging” boxes for excavation work, and, more particularly, to de-watering methods and apparatus for use in connection with such digging boxes.

BACKGROUND AND SUMMARY OF THE INVENTION

Excavation work, such as to lay drainage piping, communication lines, roadside service conduits, and the like, and to otherwise aid in construction projects, frequently involves creating a trench in the ground surface which extends several feet deep. Four to twenty foot deep trenches are not uncommon. To prevent the sides of the trench from collapsing inward while the excavation work is in progress or while the trench is in use for placement of structures therein, trench or digging boxes have been used. These boxes are typically comprised of two rigid steel side panels held apart and in fixed relationship by a plurality of steel tubes at the ends of the panels. Various such trench boxes are known, but examples can be found at the interne web site of www.shoringsolutions.com. These trench boxes can be any desired size in length, and eight to 24 foot lengths are not uncommon. The open ends of the boxes may or may not be shored with supplemental sheets of metal or plywood to prevent dirt, gravel, and debris from falling into the trench from the ends, depending upon the length of the trench box and the particular applications. Also, additional shoring may be used as a vertical extension of the trench box along the sides and/or ends thereof, according to the depth of excavation needed.

Excavation for trenches often must involve removal of water from the trench, especially where certain soil and gravel stratus would result in an accumulation of water near the surface of the ground at depths less than the bottom of the trench, but also as a result of inclement weather during trenching operations. Previously, several methods for such “de-watering” have been used. For example, wellpoint methods typically involve drilling or boring at a plurality of positions adjacent to and surrounding the trench and pumping water our of the ground to prevent that water from flowing into the trench. However, providing these wells is a significant additional excavation cost and expands the necessary “footprint” or work space needed for the trench. Also, when the trench box “moves” or is dragged to a new trench location along the path of the drainage piping, for example, the wells have to be redrilled at the new locations. Further, the well heads create restrictions in the mobility and placement of equipment used in the excavation and construction project.

Alternatively (or in addition), it has been suggested to use pumps and various hoses to remove water from the interior of the trench once the water flows into the trench. However, such equipment can get in the way of further excavation in the trench box and thereby slow down the excavation itself. Further, such equipment runs a risk of being itself damaged by the excavation equipment, such as by the bucket of a tracked excavator reaching into the trench box from the ground surface above. Also, where pumps have been installed in the interior space of the trench box, “over-excavation” techniques have been needed to put down relatively thick beds of gravel, such as one inch stone, to filter out dirt and debris from the water before it reaches the pumps, and tight sheeting of the trench box has often been used to reduce the flow of water into the trench. These techniques can result in a significant increase in excavation costs. In addition, since the hoses or conduits lowered into the interior of the trench typically have a length of perforated sleeve at the end thereof through which the water is drawn, the suction effect is lost as soon as the water level falls below the top of that sleeve and the pump starts drawing air. The water at the lower portion of the sleeve still remains in the trench.

Accordingly, it is an object of the present invention to provide an improved method and apparatus for excavating trenches. Other objects include the provision of trenching methods and apparatus which:

-   -   a. reduce the cost of excavation,     -   b. increase the effectiveness of de-watering,     -   c. reduce the space needed for the excavation work,     -   d. minimize the need for extra excavation processes,     -   e. reduce the time needed for excavation work,     -   f. increase the safety and security for persons involved in         excavation, and     -   g. reduce the risk of operational damage to excavation         equipment.

These and other objects of the present invention are obtained by the provision and use of a trenching or digging box which incorporates within its existing structure de-watering equipment that draws water into the lowermost portions of the box itself and then pumps the water out of the box. This de-watering equipment can be retrofit into existing trench boxes by modification of the existing blade or lowermost portion of the box or the addition of a blade or lowermost portion. Slots or perforations in the blade portion or lower portions of the trench box serve to filter debris in the first instance. Additional or alternative filtering can be accomplished by lengths of perforated or slotted pipes inside the walls of the trench box, especially near the lower portions of the box walls. Water can be drawn from either or both ends of the trench box. Attachments to the de-watering pump and/or the piping thereof can be used to focus de-watering and specific areas of concern to supplement the basis process. De-watering can be accomplished from one or both of the side walls of the trench box.

Other objects, advantages, and novel features of the present invention will become readily apparent to those of skill in the art from the additional description of the invention below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a rear perspective view of a schematic of a trench box incorporating the present invention into one of the side walls of the trench box.

FIG. 2 shows a rear perspective view of a schematic of a trench box incorporating the present invention into both of the side walls of the trench box, with the rear portions of the de-watering equipment exposed.

FIG. 3 shows a upper right rear perspective view of the trench box of FIG. 1.

FIG. 4 shows an upper right rear perspective view of the trench box of FIG. 2.

FIG. 5 shows an interior view of the right side of the trench box of FIG. 2, with portions of the de-watering equipment shielded.

FIG. 6 shows an interior view of the right side of the trench box of FIG. 2 with portions of the de-watering equipment exposed.

FIG. 7 shows the conduit and support portions of the de-watering equipment of FIG. 5.

FIG. 8 shows an interior right side view of a retrofitable blade extension or lower portion of a trench box incorporating the present invention for use with an existing flat bottomed trench box.

FIG. 9 shows a side view of interchangeable suction drop tubes for use with the present invention.

BRIEF DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1 and 2 show a representative trench or digging box 10 having a left side wall or panel 12 and a right side wall or panel 14 which are spaced apart at each end of the walls by structural tubes or spreader 16. The interior of the trench for working purposes is the area between side walls 12 and 14. Preferably, the bottom portion of each side wall includes a blade or tapered portion 18. The top of the trench box would normally be open, so as to allow persons and excavation equipment and/or construction equipment to enter the trench box, and the bottom of the trench box would typically rest of the exposed dirt, clay, rock and/or filtering gravel, according to the particular application, with blade 18 at the point of further penetration of the ground.

The present invention involves placing the de-watering equipment inside of the trench box structure itself, rather than inside the trench bounded by the trench box or spaced about the outside of the trench box area. In a general sense, the method of the present invention is to place the trench box in position within a trench area (that area being defined by a pre-dug trench or the location where further digging is intended and within which the trench box would settle or “sink” into position), allow water to enter portions of the trench box, preferably the lower most portions, and then pump the water out of the trench box, keeping the water from excess accumulation within the trench itself. The lower portions of the trench box are preferably in the form of a wedge or blade which can more readily penetrate the ground or gravel used at the bottom of the trench. Where the blade extends below the surface of the bottom of the trench, the water can often be prevented from having any visible accumulation in the trench itself.

Blade 18 in the drawings is shown schematically for ease of illustration. In general, a bladed lower portion of trench boxes is well known in the prior art. However, with respect to the present invention, the blade is preferably formed from sections of steel grating with a large number perforations 20 therein, such as stamped or pressed slots 0.030 inch wide. These perforations are sized and spaced so as to have no significant impact on the strength of the blade, especially where, for example, the blade is formed from ¼ inch thick steel sections four foot in length and width. Various alternative perforation of the blade or lower portion of the side walls is available for use with the present invention, depending upon the relative cost of materials in a given instance and the amount of filtering needed for the water in a given excavation. In general, however, the perforations preferably extend to virtually the bottom of the trench box side walls. Also, as shown in FIGS. 2 through 4, the perforations are preferably formed on both sides of the blade, so as to allow water to enter the trench box from outside the trench as well as inside the trench.

Inside the trench box, the present invention provides for one or more pipes or conduits to pass through the areas 22 where water is allowed to accumulate, as shown in FIGS. 6 and 7. Preferably, these pipes form a loop with solid pipe 24 positioned above perforated or slotted pipe 26. These pipes can be formed from a variety of materials, including two inch diameter PVC. Slotted pipe 26 can be formed, for example, by sawing longitudinal slots along the length of the pipe, the slots being only the width of the saw blade. The slots serve to filter debris from the water and can be used alone or in combination with textile coverings or filter media of various types, such as “Carthage 30%,” a woven monofilament geotextile of polypropylene sold by Carthage Mills. In general, the slotted pipe 26 should be placed in the trench box below where the top of the accumulation of water is expected, so as to maintain constant suction on the water.

Slotted pipe 26 is preferably formed from a plurality of perforated sections, 26 a, 26 b, 26 c, and 26 d, as shown for example. These sections are preferably interchangeable, as needed for a particular application, and can be joined together by a variety of conventional means, such as a two inch fernco or a rubber hose sleeve with band clamps at either end. For example, in a given embodiment, section 26 a at the rear of the trench box and 26 d at the front of the trench box may be the only sections with perforations in them for water to enter, the middle sections being formed from solid walled (unperforated) pipe. Alternatively, one of more of the sections can be formed with downwardly extending tubes 28 to draw water from the lowermost part of the trench box, as shown in FIG. 9. These tubes 28 are, for example, formed from metal conduit whose open ends are closed down, pinched, or crimped into a small slot 30 for water to enter. Since the tubes have a narrowed end dimension adjacent the slot, they can reach into the lowest most portions of the blade portion of the trench box.

Depending on the length of the trench box and the materials used for pipes 24 and 26, support structure 32 may be provided with the trench box, particularly at the locations where the pipe sections are joined.

In a given application, solid pipe 24 may not be needed by the present invention for de-watering. However, where it is desirable to be able to pump water from one end or the other end or both ends of the trench box, pipe 24 provides that extra functionality. Pipes 24 and 26 extend out of the lowermost portions of the trench box and into a manifold area 34. Prior to entering manifold area 34, water flow out of those pipes is controlled by a valve arrangement. In preferred embodiments, pipe 24 has a ball valve 36 adjacent the manifold area 34, and pipe 26 has a ball valve 38 adjacent the manifold area. Opening or closing these ball valves will control the extent to which water is allowed to be draw through the respective pipes and into the manifold area. For example, if ball valve 36 is open, water can be drawn first from the front of the trench box by pipe 24, and if ball valve 38 is open, water can be drawn first from the rear of the trench box by pipe 26. If both ball valves are open, then water is drawn from both ends of the trench box at the same time.

In preferred embodiments another, supplemental input conduit or pipe 40 is available into manifold area 34. Use of pipe 40 is, for example, controlled by ball valve 42. Various attachments or supplemental pump hoses can be threaded or otherwise connected to pipe 40 to provide water into manifold area 34 when ball vale 42 is open. For example, a suction well point hose or suction strainer hose can be connected to pipe 40 to allow excess water from specific or supplemental areas to be draw away by the present invention at the same time or supplemental to de-watering from the trench box lower portions.

Upstream from manifold area 34 are connections 44 to the de-watering pump, either directly or through conventional hoses, pipes, or conduits. From the pump, the water removed from the trench box is displaced to any desired location, as it would be in conventional de-watering methods. Various conventional pumps are suitable for use in the present invention. One example would be a six inch, 100 horsepower vacuum pump made by Thompson Pump, as seen at www.thompsonpump.com. Preferably, two such connections 44 are available, one extending vertically and the other horizontally, so as to provide greater flexibility of use for the present invention. For example, one of connections 44 can be used for the pump, while the other can be used to cross connect to the de-watering manifold area and/or pipes of the other side wall of the trench box. Alternatively, each side wall can have its own pump connection. If a given connection 44 is not being used, it can be readily closed by, for example, a threaded cap.

The present invention can be readily adapted to existing trench boxes by either modifying the lower portions thereof or by adding a replacement blade portions at the lower end of the side walls, as shown by FIG. 8. Also, the present invention need not be mounted in a blade portion where the lower portion of the trench box is of a different configuration, as is desired for a particular application. In general, however, it is preferable that the present invention be mounted where water can be allowed to accumulate within the trench box, and that is often at the lowest part of the trench box, and where the trench box penetrates into the ground below the bottom of the trench.

Accordingly, while the present invention has been described above in terms of preferred embodiments, it will be readily understood by those skilled in the art that those are by way of illustration and example only, and not to be taken as a limitation. The spirit and scope of the present invention are defined instead by the claims following. 

What is claimed is:
 1. A method of de-watering a trench, comprising: placing a trench box within a trench area, then allowing water to accumulate within interior of portions of the trench box, and then pumping water out of the trench box so as to prevent accumulation of water within the trench area.
 2. A trench box apparatus, for use in a trench, comprising: at least one side wall having a portion thereof which is exposed to ground water, perforations within the side wall which allow ground water to enter the side wall, a region within the side wall where ground water is allowed to collect after passing through the perforations, pumping means for removing the collected water from that region such that the water does not accumulate in the trench.
 3. The apparatus according to claim 2 wherein said region is located at the bottom portion of the trench box, the pumping means includes at least one perforated pipe placed within said region below the level where water is expected to accumulate to.
 4. The apparatus according to claim 3 wherein the pumping means is constructed to be able to selectively draw water from either the front or the rear or both ends of the trench box.
 5. The apparatus according to claim 4 wherein the perforated pipe is formed from a plurality of sections, at least one of which includes downwardly directed tubes having slotted end portions to draw water from lowermost portions of said region.
 6. The apparatus according to claim 5 wherein the pumping means includes means to draw water alternatively or in combination from accessory hoses or conduits. 